System for framing screens

ABSTRACT

A system for framing printing screens with uniform tension and deflection includes a fixture for receiving elongated resilient splines in predetermined locations. A screen is placed over the splines so that the splines define the periphery of a framed screen. A frame, channeled to receive the splines, is then placed over the screen and is compressed in the fixture to simultaneously jam the splines in the frame channels and thereby lock the screen in the frame.

United States Patent 1 [72] Inventor Georgel". Gordon 2,753,897 7/ 1956 Conrad 140/109 Nllllul, NJ]. 2,804,101 8/1957 140/109 [21] Appl. No. 662,361 2.898.951 8/1959 140/109 I [22] Filed All. 22,1967 2,844,172 7/1958 Harmon 140/109 [45 Patented Primary Examiner-Robert C. Riordon I 173] Asslgnee ham Assistant Examiner-J. C. Peters -9 Attorney-Cesari and McKenna [54] SYSTEM FOR FRAMING SCREENS 8 Claims, 3 Drawing Figs. [52] 0.8. 140/109 ABSTRACT: A system for framing printing screens with [51] III. Z uniform tension and deflection includes a fixture for receiving [50] Fit Of Search 140/109, elongated resilient splines in predetermined locations, A 108; 29/235, 448, 452 screen is placed over the splines so that the splines define the periphery of a framed screen. A frame, channeled to receive [56] Ram cud the splines, is then placed overthe screen and is compressed in UNITED STATES PATENTS the fixture to simultaneously jam the splines in the frame u lfipufig'll ms llfiz. !!!!E. a. 29/44 channels and thereby lock the'screen in the frame.

PATENTED' mm s m sum 2 [1? Fig. 2

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GEORGE F. GORDON ATTORNEYS I SYSTEM FOR FRAMING SCREENS BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to screens for printing. More particularly, it relates to techniques for framing screens used in precision printing so that screen tension and deflection are uniform.

2. Description of the Prior Art For many years silk screen printing has been widely used in the graphic arts field. Many bottles and packages can be more readily and economically labeled by silk screen techniques than by other methods.

With the advent of printed circuitry the electronics industry has sought to apply graphic arts techniques to circuit manufacturing in order to facilitate automated production. In the course of this evolution, however, photoetching techniques have, for many applications, proved to be superior to screening. A principal reason for this is that the typical graphic arts screening techniques have proved to be insufficiently precise for electronic applications. With the boom in integrated circuit usage rapidly approaching, great precision in printing techniques is now in demand. To satisfy this need various approaches have been used. Of those in the field of silk screening, one such approach involves stretching the screen on a frame and retaining it under tension with brackets held by screws. This technique requires a substantial amount of skilled hand labor, thereby making it somewhat costly. Another approach involves securing prestretched screen in a frame with a suitable adhesive, such as an epoxy resin. This too, however, is not readily subject to automation.

A somewhat simpler method of making silk screens involves the use of a frame having a channel about its periphery. The screen is stretched over the frame and secured in position by manually jamming elongated resilient splines into the frame channel, thereby locking the screen into the frame. Since the screen is locked into the frame one side at a time, however, it is exceedingly difficult'to maintain the screen tension uniform in all directions. In other words, if the screen is first stretched in one direction and clinched into the frame, it is difficult to stretch the screen in the transverse direction by exactly the same amount. Failure to do this often results in a waviness of the screen threads which can militate against the sharpness of SUMMARY OF THE INVENTION Briefly, my technique for framing printing screens involves placing elongated resilient splines on a fixture so that the splines define the periphery of a finished screen. I then place a screen over the splines so that the screen edges extend beyond the splines and so that the working area of the screen is bounded by the splines. Following this, I place a frame over the screen and splines so that the splines are in register with channels or grooves in the frame. With the elements in this position I then compress the frame and screen in the fixture. This causes the splines to be simultaneously jammed into the channels in the frame where they lock the screen into the frame. By. simultaneously locking the screen into the frame around its entire periphery, the screen is placed under substantially uniform tension in all directions.

To facilitate my technique for framing screens I use a fixture which has a base with a member resiliently supported in a plane parallel to the base. This member is free to move toward and away from the base. Rigid thin plates, secured to thebase, extend perpendicular to the base and substantially surround that member. The resiliently supported member is so shaped that it provides for support of a screen and frame and alignment of the screen with respect to the frame. When splines or similar retaining elements are placed! on the edges of the rigid plates, and a screen and frame are properly positioned on the member, the fixture is placed in a press and compressed. The pressing operation forces the member toward the base. The screen edge and frame then contact the splines supported by the rigid plates and the splines are jammed by the plates into the channels or grooves in the frame, thereby locking the screen into the frame as pointed out above. Use of this fixture enables the fabrication of virtually any number of successive screens of the same type with uniform tension in all directions,

and with uniform screen deflection.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. I is a perspective view exploded and partly in section of the fixture used In the technique of my invention;

FIG. 2 is an elevational section of a portion of the fixture of FIG. 1; and

FIG. 3 is an elevational sectionof the portion of the device illustrated in FIG. i! but the compressed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Of the various methods of producing screens for precision printing, I have found that one of the simplest and most efficient ones involves the use of a frame having channels or grooves in its periphery. The screen is locked into such a frame by means of elongated resilient splines or gaskets jammed with the screen into the channels or grooves. As used herein the term screen refers to any foraminous material, as for example a woven screen, expanded metal or an etched metal mask. Also, as I refer to the use of splines for insertion into frame channels or grooves, I intend this term to include tubes, rods or other elongated somewhat resilient elements suitable for engagement with such grooves or channels.

Broadly, my method involves clinching the screen into a frame simultaneously about its entire periphery. If, for example, a rectangular screen and rectangular frame are used, it involves clinching all four edges of the screen to the frame at once.

In practice I accomplish this by means of a special fixture. First, if the screen is to be rectangular, I place four elongated splines on the fixture to define the screen periphery. I then place the screen on the fixture with the screen edges overlapping each of these elongated splines. Following this, I place a frame in contact with the screen. The frame has a channel or groove around its periphery. The groove is in register with the four elongated splines. I then compress the frame and fixture so that the splines and screen are driven simultaneously into the groove of the frame. This locks the screen into the frame so that there is uniform tension on the screen in both right angle axes of the frame plane. By suitably tailoring such parameters as the groove depth in the frame, any desired predetermined tension can be achieved.

FIXTURE A preferred embodiment of a fixture useful in the screen framing technique of my invention :is illustrated in the exploded view of FIG. 1. The fixture includes a base 10 having four block members 12 secured thereto by bolts M. The block members 12 support rigid plates 16 and secure them in a position perpendicular to the base 10.

Supported above each block member 12 is an edge bracket 18. The edge brackets 18 have hinged flaps 20.

Within the area bounded by the plates l6'are four spring biased posts 22 that are axially movable within preset limits. The posts have caps 23 with projections 25. Four positioning guides 24 have dogs 26 extending at right angles thereto. The dogs 26 ride in slots 28 that are defined by the edges of the plates 16. The ends of the dogs 26 rest upon the caps 23.

A platform 30 for supporting a screen in the fixture has its four corners 32 resting upon the dogs 26. Small apertures 33 in the platform 30 engage the projections to maintain the platform in alignment. The platform has a large aperture 34 therein which may be useful in lining up the screen threads to assure that the screen threads are parallel to the frame 36 edges. A transparent lens having reticles may be placed in the aperture 34 and made a part of the platform 30. The use of the reticles enables a user to determine whether the screen threads are at right angles to one another. This also aids in assuring that the screen is positioned on the platform 30 so that as the frame 36 is lowered onto the platform 30 the screen threads are parallel to the edges of the frame 36.

The operation of the fixture is more readily understood by reference to FIGS. 2 and 3. Here the elements are assembled in position in preparation for securing a screen 38 into the frame 36. Before placing the screen 38 on the platform 30, resilient splines or gaskets 40 are placed on the exposed edges 42 of the plates 16. Following the positioning of the screen 38 on the platform 30, the frame 36 is placed on the screen so that the grooves or channels 44 are in register with the splines 40. With the elements so positioned, the fixture is placed in a press. In FIG. 3 the fixture is illustrated in a press with the press platen 46 exerting pressure on the frame 36. In this position the frame 36 has forced down the platform 30 and edge bracket 18 compressing the springs 48 and 50, respectively. As a result of the compression the splines 40 are forced into the grooves 44. This creates a tension on the screen 38 and locks or clinches it into the screen frame 36. The hinged flaps 20 are also pressed down by the frame 36 and are used with some screens to restrain the loose ends 52 of the screen 38. As the splines 40 are jammed into the grooves 44, tension is placed on the screen portion within the frame since the loose ends of the screen are secured by the flaps 20.

From the operation of the fixture it is apparent that the screen tension is a function of the depth of the grooves 44, the degree of restraint on the screen ends 52 and the amount of tension on the screen 30 prior to the moment when it is clinched into the frame 36. The screen deflection, on the other hand, is more a function of the diameter of the mesh than of the tension.

As a practical matter, to produce screens of high precision it is necessary that the screen frames be absolutely planar, that the screen threads be at right angles to one another, that the screen have uniform tension in both directions and that the screen deflection be uniform from one screen to the next of the same type. Each ofthese features is achieved by my screen framing system.

Frames, such as the frame 36, may be manufactured by casting suitable metals or alloys and grinding off the flashing so that the frame fits properly into the fixture. The screens may be made from expanded metals or mesh such as stainless steel.

In one particularly useful embodiment of my technique, I secure a solid piece of sheet metal in the screen frame, as, for example, a 2 mil sheet of molybdenum. With the piece of sheet metal properly tensioned in the frame, I etch the desired pattern, such as an integrated circuit, on one side of the sheet metal and then etch the mesh on the other side. This two-sided etching technique provides screens having a printing resolution equal to or better than the conventional woven screens.

It will thus be seen that the objects'set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above process and in the construction set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

lclaim:

l. A fixture for framing printing screens with uniform tension and deflection comprising:

A. a base;

B. a support member arranged and adapted to support a printing screen and its frame;

C. means connecting the support member to the base so that the support member is free to move toward and away from the base;

D. means projecting up from the base, said projecting means at least partially surrounding the support member and defining at least one slot extending up from the base;

E. edge brackets;

F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting means;

G. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and

H. means on the support member for riding in the slot so as to maintain the support in the proper position when it is moved toward and away from the base.

2. The fixture of claim 12 wherein the support member is rectangular and the projecting means comprise four plates arranged on edge and substantially surrounding the support member.

3. A fixture for framing printing screens as defined in claim 1 wherein the engaging means comprise flaps hinged to the brackets, the edge of each flap opposite the hinge being positioned adjacent a projecting means so that when a printing screen is supported on the supporting means, the flaps overhang the periphery of the screen and when a frame is also supported on the supporting means, the frame presses the flaps down against the screen so that the screen is held in proper alignment.

4. A fixture according to claim 1 wherein the support member and edge brackets are resiliently supported above the base.

5. A fixture for framing printing screens with uniform tension and deflection comprising:

A. a base;

B. a support member arranged and adapted to support a printing screen and its frame;

C. means connecting the support member to the base so that the support member is free to move toward and away from the base;

D. means projecting up from the base, said projecting means at least partially surrounding the support member;

E. guide means connected to the periphery of the support member; and

F. means connected to the base for receiving the guide means, said receiving means defining an extending perpendicular to the base and in register with the guide means so that the support member is maintained in the proper position when it is moved toward or away from the base.

6. A fixture for framing printing screens as defined in claim 5 and further including reticles on the support member for facilitating alignment of a printing screen on the support member.

7. A fixture for framing printing screens with uniform tension and deflection comprising:

A. a base;

B. a support member arranged and adapted to support a printing screen and its frame;

C. means connecting the support member to the base so that the support member is free to move toward and away from the base; v

D. means projecting up from the base, said projecting means at least partially surrounding'the support member and defining at least one slot extending up from the base;

E. edge brackets; y

F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting means;

i 0. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and j H. reticles on the support member for facilitating alignment of a printing screen on the support member.

8. A fixture for framing printing screens with uniform tension and deflection comprising:

A. a base; a

B. a support member arranged and adapted to support a printing screen and its frame;

C. means connecting the support member to the base so that the support member is free to move toward and away from the base;

D. means projecting up from the base, said projecting means at least partially surrounding the support member and defining at least one slot extending up from the base;

E. edge brackets;

F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting :means;

G. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and a H. said engaging means comprising flaps hinged to the brackets, the edge of each flap opposite the hinge being positioned adjacent a projecting means so that when a printing screen is supported on the support member, the flaps overhang the periphery of the screen and when a frame is also supported on the supporting member, the frame presses the flaps down against the screen so that the screen is held in proper alignment. 

1. A fixture for framing printing screens with uniform tension and deflection comprising: A. a base; B. a support member arranged and adapted to support a printing screen and its frame; C. means connecting the support member to the base so that the support member is free to move toward and away from the base; D. means projecting up from the base, said projecting means at least partially surrounding the support member and defining at least one slot extending up from the base; E. edge brackets; F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting means; G. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and H. means on the support member for riding in the slot so as to maintain the support in the proper position when it is moved toward and away from the base.
 2. The fixture of claim 12 wherein the support member is rectangular and the projecting means comprise four plates arranged on edge and substantially surrounding the support member.
 3. A fixture for framing printing screens as defined in claim 1 wherein the engaging means comprise flaps hinged to the brackets, the edge of each flap opposite the hinge being positioned adjacent a projecting means so that when a printing screen is supported on the supporting means, the flaps overhang the periphery of the screen and when a frame is also supported on the supporting means, the frame presses the flaps down against the screen so that the screen is held in proper alignment.
 4. A fixture according to claim 1 wherein the support member and edge brackets are resiliently supported above the base.
 5. A fixture for framing printing screens with uniform tension and deflection comprising: A. a base; B. a support member arranged and adapted to support a printing screen and its frame; C. means connecting the support member to the base so that tHe support member is free to move toward and away from the base; D. means projecting up from the base, said projecting means at least partially surrounding the support member; E. guide means connected to the periphery of the support member; and F. means connected to the base for receiving the guide means, said receiving means defining an extending perpendicular to the base and in register with the guide means so that the support member is maintained in the proper position when it is moved toward or away from the base.
 6. A fixture for framing printing screens as defined in claim 5 and further including reticles on the support member for facilitating alignment of a printing screen on the support member.
 7. A fixture for framing printing screens with uniform tension and deflection comprising: A. a base; B. a support member arranged and adapted to support a printing screen and its frame; C. means connecting the support member to the base so that the support member is free to move toward and away from the base; D. means projecting up from the base, said projecting means at least partially surrounding the support member and defining at least one slot extending up from the base; E. edge brackets; F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting means; G. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and H. reticles on the support member for facilitating alignment of a printing screen on the support member.
 8. A fixture for framing printing screens with uniform tension and deflection comprising: A. a base; B. a support member arranged and adapted to support a printing screen and its frame; C. means connecting the support member to the base so that the support member is free to move toward and away from the base; D. means projecting up from the base, said projecting means at least partially surrounding the support member and defining at least one slot extending up from the base; E. edge brackets; F. means connecting the edge brackets to the base so that the edge brackets are free to move toward and away from the base adjacent the projecting means; G. means on the edge brackets for releasably engaging a screen supported on the support member so as to maintain the screen in proper alignment relative to the projecting means; and H. said engaging means comprising flaps hinged to the brackets, the edge of each flap opposite the hinge being positioned adjacent a projecting means so that when a printing screen is supported on the support member, the flaps overhang the periphery of the screen and when a frame is also supported on the supporting member, the frame presses the flaps down against the screen so that the screen is held in proper alignment. 